I'm pretty sure it requires JASS.
And I'm pretty sure it has something to do with making the model hover, then fly...and back. But then again I could be wrong.
Anyways I'm pretty sure that it is just editing the unit's elevation...

u could do it in gui if u used a unit with a animation with a jump (like bm) by changing the unit into a projectile aimed at an enemy then place bm unit by the enemy and remove the bm from game whilst the spell is in play

Idk about doing back flips but if u want to jump u ould just make basicly a slide trigger and a unit elevation tigger. Instead of ones that just change unit elevation and make it look like your running if u do that then the units feet won't move and it looks like its really jumping if u want i can try to make a map that shows how it would work..

I am sure there is a spell made in Jass or Gui ...I even used one but didn't use it for a backfilp.
But there is also a model of a footman that can do a backflip its based on the model of the headhunter(Orc)